1. Field of the Invention
The invention relates to a vehicle backward movement detection apparatus and a vehicle braking force control apparatus. More particularly, the invention relates to a vehicle backward movement detection apparatus which detects backward movement of a vehicle on a hill, and a vehicle braking force control apparatus which performs braking based on that detected backward movement.
2. Description of the Related Art
A vehicle braking force control apparatus is disclosed in Japanese Patent Application Publication No. JP-A-2002-264784, for example. This vehicle braking force control apparatus increases the braking force when a vehicle body acceleration rate is greater than a predetermined value in order to stop the vehicle from moving backwards. A wheel speed sensor is used to detect the vehicle body acceleration rate.
At low speeds equal to, or less than, the detection limit of the wheel speed sensor, however, it is difficult to accurately detect the vehicle body speed and acceleration rate when the vehicle is moving backwards. Accordingly, it is also difficult to accurately control the braking force using the sensor output. In addition, it is difficult to control an increase and decrease in braking force when the vehicle body is on a road with a low μ, which often results in hunting.